symbian-qemu-0.9.1-12/python-win32-2.6.1/lib/shelve.py
author John Kern <johnk@symbian.org>
Tue, 08 Dec 2009 11:07:49 -0800
changeset 23 8374da225e88
parent 1 2fb8b9db1c86
permissions -rw-r--r--
fix for S^2 builds
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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"""Manage shelves of pickled objects.
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A "shelf" is a persistent, dictionary-like object.  The difference
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with dbm databases is that the values (not the keys!) in a shelf can
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be essentially arbitrary Python objects -- anything that the "pickle"
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module can handle.  This includes most class instances, recursive data
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types, and objects containing lots of shared sub-objects.  The keys
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are ordinary strings.
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To summarize the interface (key is a string, data is an arbitrary
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object):
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        import shelve
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        d = shelve.open(filename) # open, with (g)dbm filename -- no suffix
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        d[key] = data   # store data at key (overwrites old data if
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                        # using an existing key)
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        data = d[key]   # retrieve a COPY of the data at key (raise
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                        # KeyError if no such key) -- NOTE that this
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                        # access returns a *copy* of the entry!
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        del d[key]      # delete data stored at key (raises KeyError
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                        # if no such key)
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        flag = d.has_key(key)   # true if the key exists; same as "key in d"
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        list = d.keys() # a list of all existing keys (slow!)
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        d.close()       # close it
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Dependent on the implementation, closing a persistent dictionary may
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or may not be necessary to flush changes to disk.
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Normally, d[key] returns a COPY of the entry.  This needs care when
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mutable entries are mutated: for example, if d[key] is a list,
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        d[key].append(anitem)
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does NOT modify the entry d[key] itself, as stored in the persistent
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mapping -- it only modifies the copy, which is then immediately
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discarded, so that the append has NO effect whatsoever.  To append an
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item to d[key] in a way that will affect the persistent mapping, use:
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        data = d[key]
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        data.append(anitem)
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        d[key] = data
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To avoid the problem with mutable entries, you may pass the keyword
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argument writeback=True in the call to shelve.open.  When you use:
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        d = shelve.open(filename, writeback=True)
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then d keeps a cache of all entries you access, and writes them all back
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to the persistent mapping when you call d.close().  This ensures that
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such usage as d[key].append(anitem) works as intended.
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However, using keyword argument writeback=True may consume vast amount
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of memory for the cache, and it may make d.close() very slow, if you
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access many of d's entries after opening it in this way: d has no way to
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check which of the entries you access are mutable and/or which ones you
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actually mutate, so it must cache, and write back at close, all of the
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entries that you access.  You can call d.sync() to write back all the
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entries in the cache, and empty the cache (d.sync() also synchronizes
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the persistent dictionary on disk, if feasible).
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"""
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# Try using cPickle and cStringIO if available.
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try:
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    from cPickle import Pickler, Unpickler
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except ImportError:
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    from pickle import Pickler, Unpickler
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try:
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    from cStringIO import StringIO
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except ImportError:
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    from StringIO import StringIO
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import UserDict
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__all__ = ["Shelf","BsdDbShelf","DbfilenameShelf","open"]
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class _ClosedDict(UserDict.DictMixin):
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    'Marker for a closed dict.  Access attempts raise a ValueError.'
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    def closed(self, *args):
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        raise ValueError('invalid operation on closed shelf')
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    __getitem__ = __setitem__ = __delitem__ = keys = closed
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    def __repr__(self):
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        return '<Closed Dictionary>'
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class Shelf(UserDict.DictMixin):
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    """Base class for shelf implementations.
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    This is initialized with a dictionary-like object.
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    See the module's __doc__ string for an overview of the interface.
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    """
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    def __init__(self, dict, protocol=None, writeback=False):
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        self.dict = dict
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        if protocol is None:
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            protocol = 0
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        self._protocol = protocol
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        self.writeback = writeback
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        self.cache = {}
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    def keys(self):
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        return self.dict.keys()
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    def __len__(self):
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        return len(self.dict)
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    def has_key(self, key):
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        return key in self.dict
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    def __contains__(self, key):
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        return key in self.dict
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    def get(self, key, default=None):
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        if key in self.dict:
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            return self[key]
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        return default
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    def __getitem__(self, key):
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        try:
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            value = self.cache[key]
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parents:
diff changeset
   120
        except KeyError:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   121
            f = StringIO(self.dict[key])
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   122
            value = Unpickler(f).load()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   123
            if self.writeback:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   124
                self.cache[key] = value
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   125
        return value
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   126
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   127
    def __setitem__(self, key, value):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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diff changeset
   128
        if self.writeback:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   129
            self.cache[key] = value
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   130
        f = StringIO()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   131
        p = Pickler(f, self._protocol)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   132
        p.dump(value)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   133
        self.dict[key] = f.getvalue()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   134
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   135
    def __delitem__(self, key):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   136
        del self.dict[key]
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   137
        try:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   138
            del self.cache[key]
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   139
        except KeyError:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   140
            pass
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   141
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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diff changeset
   142
    def close(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   143
        self.sync()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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diff changeset
   144
        try:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
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diff changeset
   145
            self.dict.close()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   146
        except AttributeError:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   147
            pass
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   148
        self.dict = _ClosedDict()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   149
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   150
    def __del__(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   151
        if not hasattr(self, 'writeback'):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   152
            # __init__ didn't succeed, so don't bother closing
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   153
            return
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   154
        self.close()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   155
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   156
    def sync(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   157
        if self.writeback and self.cache:
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   158
            self.writeback = False
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   159
            for key, entry in self.cache.iteritems():
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   160
                self[key] = entry
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   161
            self.writeback = True
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   162
            self.cache = {}
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   163
        if hasattr(self.dict, 'sync'):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   164
            self.dict.sync()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   165
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   166
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   167
class BsdDbShelf(Shelf):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   168
    """Shelf implementation using the "BSD" db interface.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   169
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   170
    This adds methods first(), next(), previous(), last() and
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   171
    set_location() that have no counterpart in [g]dbm databases.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   172
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   173
    The actual database must be opened using one of the "bsddb"
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   174
    modules "open" routines (i.e. bsddb.hashopen, bsddb.btopen or
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   175
    bsddb.rnopen) and passed to the constructor.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   176
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   177
    See the module's __doc__ string for an overview of the interface.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   178
    """
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   179
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   180
    def __init__(self, dict, protocol=None, writeback=False):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   181
        Shelf.__init__(self, dict, protocol, writeback)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   182
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   183
    def set_location(self, key):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   184
        (key, value) = self.dict.set_location(key)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   185
        f = StringIO(value)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   186
        return (key, Unpickler(f).load())
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   187
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   188
    def next(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   189
        (key, value) = self.dict.next()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   190
        f = StringIO(value)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   191
        return (key, Unpickler(f).load())
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   192
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   193
    def previous(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   194
        (key, value) = self.dict.previous()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   195
        f = StringIO(value)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   196
        return (key, Unpickler(f).load())
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   197
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   198
    def first(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   199
        (key, value) = self.dict.first()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   200
        f = StringIO(value)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   201
        return (key, Unpickler(f).load())
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   202
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   203
    def last(self):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   204
        (key, value) = self.dict.last()
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   205
        f = StringIO(value)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   206
        return (key, Unpickler(f).load())
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   207
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff changeset
   208
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   209
class DbfilenameShelf(Shelf):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   210
    """Shelf implementation using the "anydbm" generic dbm interface.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   211
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   212
    This is initialized with the filename for the dbm database.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   213
    See the module's __doc__ string for an overview of the interface.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   214
    """
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   215
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   216
    def __init__(self, filename, flag='c', protocol=None, writeback=False):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   217
        import anydbm
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   218
        Shelf.__init__(self, anydbm.open(filename, flag), protocol, writeback)
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   219
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   220
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   221
def open(filename, flag='c', protocol=None, writeback=False):
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   222
    """Open a persistent dictionary for reading and writing.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   223
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   224
    The filename parameter is the base filename for the underlying
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   225
    database.  As a side-effect, an extension may be added to the
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   226
    filename and more than one file may be created.  The optional flag
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   227
    parameter has the same interpretation as the flag parameter of
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   228
    anydbm.open(). The optional protocol parameter specifies the
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   229
    version of the pickle protocol (0, 1, or 2).
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   230
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   231
    See the module's __doc__ string for an overview of the interface.
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   232
    """
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   233
2fb8b9db1c86 Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff changeset
   234
    return DbfilenameShelf(filename, flag, protocol, writeback)